Field of the Invention
This disclosure relates to a sheet feeding apparatus and an image forming apparatus, and particularly, to a configuration for detecting sizes of sheets stored in a storage cassette.
Description of the Related Art
In the related art, in an image forming apparatus such as a printer, a sheet feeding apparatus for feeding a sheet to an image forming portion is provided.
The sheet feeding apparatus includes a sheet feeding cassette which is mounted on an apparatus body and in which sheets are stored, and a sheet feeding portion that feeds the sheets stored in the sheet feeding cassette.
The sheet feeding cassette can store sheets having different sizes and if such a sheet feeding cassette is used, a control portion of the image forming apparatus is necessary to determine the size of the sheet in advance to form an appropriate image on the sheet. Thus, in the related art, a sheet feeding apparatus is provided with a size detection sensor for detecting the size of the sheet stored in the sheet feeding cassette. When the sheet feeding cassette is mounted on the apparatus body, the size of the sheet is detected by the size detection sensor.
As the size detection sensor, a sensor has been known which includes a plurality of size detection levers pivoting in accordance with a movement of a regulating plate provided in the sheet feeding cassette to regulate side ends of the sheet and a plurality of detection elements which are disposed on an apparatus body side and which are turned ON/OFF in accordance with pivoting positions of the size detection levers.
Then, when the regulating plate is moved to a position corresponding to the sheet size, and the size detection levers are pivoted to predetermined positions in accordance with the movement of the regulating plate. Thus, if the sheet feeding cassette is mounted on the apparatus body, the size detection levers selectively perform ON/OFF of the detection elements. ON/OFF signals of the detection elements are transmitted to the control portion and the control portion detects the size of the sheet stored in the sheet feeding cassette based on a combination of the ON/OFF signals.
However, in the related art, as described in JP-A-2010-173806, a detection element has been known employing an inexpensive contact type switch. Here, the contact type switch protrudes toward the sheet feeding cassette by a biasing member such as a spring until the contact switch is pressed by the size detection levers. Furthermore, a mounting base holding the contact type switch is also supported to be movable (floating state) and is biased in a protrusion direction of the contact type switch by the biasing member such as the spring.
Thus, in order to operate the switch, the mounting base and the switch have to be pressed by the size detection levers against the biasing force by the biasing member and a large operation force (pressing force) is required when mounting the sheet feeding cassette. In addition, even if the size detection levers are in positions where the size detection levers press the switch, the switch cannot be reliably pressed due to the shape of a contact portion of the size detection levers and the switch or mounting backlash, and the like. In this case, it is not possible to accurately detect the size of the sheet.
Thus, as the detection element, a non-contact type sensor, for example, a photo sensor may be used. In this case, since the lever does not come into contact with the photo sensor, it is possible to reduce the operation force. In addition, since it is a non-contact type, it is possible to prevent erroneous detection of the size of the sheet due to the shape of the contact portion of the size detection levers and the switch, or mounting backlash, and the like as when using the contact type switch.
However, light emitted from a light-emitting portion is received by a light receiving-portion or is shielded by a light shielding portion, and thereby in such a manner the photo sensor is intended to be turned ON/OFF. Thus, for example, in a case where the light shielding portion is provided in the size detection levers, if the sheet feeding cassette and the size detection levers are not accurately positioned when mounting the sheet feeding cassette, it is not possible to accurately detect the sheet size.